Modicon Internal Logic

Have a question about Quantum ModiconPLCS. Got to work with them for the first time the last couple of days on a plant in the middle of the aussie desert a long, long way from anyway.

The system consists of Modicon Plcs, with a RS3 Rosemount DCS for graphics and analogue outputs. Analogue inputs and all discretes go to the PLCs.

Question is regarding addressing. I worked out that
0x was for digital outputs
1x was for digital inputs
3x was for analogue inputs
4x was for registers

but ran into a little prob when trying to work out the internal logic address. Took awhile but I appear to have found in the 0x data tables further down. Is this the common and best way to do it? Also, if the PLCs had analogue outputs would they be addressed in the 3x table?

Couldnt find any help on this addressing question on the online help function, ProWorx NxT is the software I used.

Ta for any help!

If you are using Proworx NxT then yes, the 0x registers are used for internal logic. The general practice is to set aside the first 500, 1000, 2000 (or however many bits you are likely to need if your plant doubles or triples in size) for outputs.
All bits from say 0:02001 and upwards are interternal bits and not used for anything else.
It is possible in the Quantum to mix internal and output bits in the same memory area, example 0:00000 to 0:00031 are outputs, 0:00032 to 0:00063 are internals, 0:00064 to 0:00095 are outputs. But obviously this is only going to get you into trouble.

If you are using Concept, you can either use 0x bits for your internals, or you can declare variables. Variables don't need any address, but cannot be used with 984 ladder logic.

Second part, Analog outputs are addressed from the 4x registers. Normally you set this up the same as the 0x register with the lower 4x registers for real outputs and the higher registers for internal storage and manipulation of integers and words. Also in some cases the 4x registers are used for inputs as well, such as from external modbus/modbus plus, profibus and ethernet devices.
The 3x table is used only for inputs, such as analogs, high speed counters and possibly the ASCII modules (can't actually remember this one).

HTH Doug

Thanks Doug great stuff!